Can We Build a Bicycle That Uses Compressed Air for Energy?

[Apache]

Can I ask you about some opinions?

We desired to build a bicycle.
That is we convert our mechanical energy to electricity energy and stored in capacitor by dynamo.
Then when it reaches certain value we discharge it and connected to the portable air compressor.
The electricty drive the compressor to suck in the air and compressed it to high pressure air that is stored inside the gas tank.
When the gas tank is charged, the high pressure air is discharged and push the piston that is connected to the crankshaft that convert linear motion to circular motion hence drive bicycle's rear wheel.
This help to save energy for long distance traveling and slope difficulty.

Is it a possible and workable idea?

Thanks ya!

 

[jedishrfu]

I'm sure you could make it workable but I think there's a lot of places where energy is lost meaning the efficiency of the device. You're going from ME to EE to capacitor to compressing air to discharging air to pushing a piston to spinning a drive shaft.

I do like the idea of converting thru all these different type kind like a rube-goldberg machine.

Wouldn't it be simpler if you used a flywheel or a windup spring to store your ME directly?

 

[Travis_King]

Yea, it would make for an interesting and probably exciting-to-build project, but it would be horribly inefficient compared to the alternatives (alternator charges a battery, battery powers an electric motor when needed).

It's workable, sure, but keep in mind that the assembly is going to be heavy, heavy, heavy for a bicycle.

 

[Simon Bridge]

I read this a little differently ... the basic concept is to divert some of the energy pedalling the bike to be stored for later use. This makes the bike harder to pedal normally and you won't get all the diverted energy back later. Even if the machine to do the diverting, storage, etc., were perfect, and could be constructed so as to add no mass to the bike, the rider would still lose overall compared with not having the device.

At best you are making hills easier (on a long ride) at the expense of making the ride harder overall. There may be some attraction is the ride is almost all flat with a few hills...

Another way to think, though, is to divert some energy from braking and free-wheeling down hills, to some storage device... Here, the first hill costs you - but part of that cost makes all subsequent hills easier without a penalty on normal riding.

How does that sound to you?

 

[jedishrfu]

I read this a little differently ... the basic concept is to divert some of the energy pedalling the bike to be stored for later use. This makes the bike harder to pedal normally and you won't get all the diverted energy back later. Even if the machine to do the diverting, storage, etc., were perfect, and could be constructed so as to add no mass to the bike, the rider would still lose overall compared with not having the device.

At best you are making hills easier (on a long ride) at the expense of making the ride harder overall. There may be some attraction is the ride is almost all flat with a few hills...

Another way to think, though, is to divert some energy from braking and free-wheeling down hills, to some storage device... Here, the first hill costs you - but part of that cost makes all subsequent hills easier without a penalty on normal riding.

How does that sound to you?

Thats a good way to look at it. The fly wheel approach works well in this scheme.

 

[Simon Bridge]

One of these...
http://www.electricbikes.co.nz/
... with the ability to charge the battery off surplus motion?
Wonder what it would take... I looked for, but did not find, a bike that does that.

 

[Travis_King]

A flywheel with enough mass and spin to be of any measurable use would make turning the bicycle very difficult. It would probably be a much bigger hassle than it's worth to you in energy savings.

 

[Simon Bridge]

Huh - mount the flywheel horizontally?
Use two, counter-rotating, flywheels?
May be worth doing the math - how much energy are we talking about?

Use a different energy store method?

 

[StrayCatalyst]

If you're using electricity anywhere in the system, why not use a PMDC motor (which, by its very nature, produces electricity when turned by an outside force) and store power in an ultracapacitor or similar? It's low power, but rapidly recharges, and has a power to weight ratio that's remarkably good.
Compressed air - you need a fairly large, heavy tank, which if it bursts, will be no more than two feet (60 cm) from your legs and groin. Flywheels would make the bike hard to turn. You might want to pick a method of storing energy that's not prone to catastrophic release if the bike crashes or is dumped.